The fireworks that delight crowds during celebrations like the Fourth of July create more than just dazzling colors. They produce smog, too.
Fireworks can generate ground-level ozone - a key ingredient in urban smog, say a group of scientists in India. They reached their conclusion after monitoring air quality during a Hindu festival when celebrants flooded New Delhi's streets to ignite sparklers.
Previously, the interaction of sunlight and air pollutants had been the only known source of ground-level ozone, which health officials say poses a threat to people with respiratory problems.
But researchers from Jawaharlal Nehru University in New Delhi found that the flickering light emitted by sparklers during the festival in November 1999 was enough to cause an atmospheric reaction that produced ozone.
The findings could raise concerns among air-quality experts, particularly because big fireworks displays often occur during the peak summer ozone season. The research appears in today's issue of the journal Nature.
But in the Los Angeles area, a notoriously smoggy part of the US, fireworks remain low on the priority list of air-quality experts. That's because the ozone increase detected in New Delhi - about 9 parts per billion - is minuscule compared with ozone produced in L.A. due to auto pollution. Los Angeles recorded a peak of 180 p.p.b. of ozone in 1999, far above the Environmental Protection Agency's maximum of 124 p.p.b.
Air-quality experts with the EPA declined to comment on the study because they had too many questions about the researchers' methodology.
"There just wasn't enough information for them to make a judgment on the validity of the study," says EPA spokesman Dave Ryan.
He said the EPA has no regulations governing fireworks displays, although the Clean Air Act permits state and local governments to enact such restrictions.
(c) Copyright 2001. The Christian Science Monitor